1. Technical Field
The present disclosure relates to photoelectric switch control circuits, and more particularly to an photoelectric switch control circuit which decreases operation errors.
2. Description of Related Art
FIG. 1 is a schematic circuit diagram of a conventional photoelectric switch control circuit. The photoelectric switch control circuit 10 is connected to a processing circuit 20, to generate logic low (level) or logic high (level) to the processing circuit 20.
The processing circuit 20 performs functions corresponding to the logic low or logic high. The photoelectric switch control circuit 10 includes a first resistance 100, a photoelectric switch 200 and a first capacitance 300. The photoelectric switch 200 having a plurality of contacts which comprise a first to a fourth contacts. The first and the fourth contacts are grounded. One end of the first resistance 100, the second and the third contacts of the photoelectric switch 200 and one end of the first capacitance 300 connects at node A. A voltage of the node A is sent to the processing unit 20 to control the processing circuit 20 to perform functions. The other end of the first resistance 100 is connected with a voltage source Vcc. The other end of the first capacitance 300 is grounded. After the voltage source Vcc is connected, a plurality of light emitting devices connected between the first and the second contacts emit infrared light, a plurality of light detecting devices connected between the third and the fourth contacts detect the infrared light. The third and the fourth contacts are connected together when the infrared light is detected, thereby node A is grounded to generate the logic low to the processing circuit 20. The third and the fourth contacts are disconnected when the infrared light is not detected, thereby node A is connected to the voltage source Vcc to generate the logic high to the processing circuit 20. The first resistance 100 is used to adjust power between the first and the second contacts of the photoelectric switch 200. The first capacitance 300 is used to filter the voltage source Vcc to enable a stable voltage between the first and the second contacts of the photoelectric switch 200.
However, a barrier voltage of a PN junction diode exists between the third and the fourth contacts of the photoelectric switch control circuit 10, even if the third and the fourth contacts are connected together. The node A is easily to be recognized to generate the logic high when the third and the fourth contacts are connected together, which makes the processing unit performs the wrong functions.